diff -r d9a3d23cf8f0 Objects/bytearrayobject.c
--- a/Objects/bytearrayobject.c	Tue Oct 14 00:53:13 2014 +0200
+++ b/Objects/bytearrayobject.c	Tue Oct 14 18:26:40 2014 +0200
@@ -200,7 +200,7 @@
         return -1;
     }
 
-    if (size + logical_offset + 1 < alloc) {
+    if (size < alloc && logical_offset + 1 < alloc - size) {
         /* Current buffer is large enough to host the requested size,
            decide on a strategy. */
         if (size < alloc / 2) {